Warhead defense systems served as protective measures found on smaller spacecraft like starfighters and light freighters, with the intention of safeguarding the vessel from approaching warheads. These systems existed in at least three forms: antimissile missiles, chaff, and flares.
The game Star Wars: X-Wing Alliance introduced countermeasures as a way for players to defend their ships against enemy warheads. Each type operated differently, presenting unique strengths and weaknesses. However, they seem primarily to be a gameplay element, receiving only brief mention in Legacy of the Force: Bloodlines and no other sources. While this doesn't negate the possibility of them being standard equipment on many small ships, as implied by Star Wars: X-Wing Alliance, they simply lack explicit confirmation.